Some oil-bearing formations, such as some of those found in Louisiana and Texas and in offshore waters of the Gulf of Mexico, are unstable including unconsolidated and/or thief formations. When drilling oil and gas wells borehole instability problems can occur including sloughing, stuck pipe and lost circulation. Thus, drilling in these formations can be difficult, expensive and time consuming.
Methods suggested for dealing with some of the problems with unstable formations including the use of lost circulation materials, cementing loss zones and setting casing through the zones. However, it remains a challenge to drill in unstable formations.